The present invention relates to a cutting method for an inner circumferential face and an outer circumferential face of a work using a cutting tool of a main shaft which turns around a predetermined position serving as a center and for which a turning radius is adjustable, the cutting being performed by making a cutting velocity of the cutting tool constant.
The “turning of the main shaft” is not limited to rotation of the main shaft along a central axis thereof but refers to rotations including revolution of the main shaft around the predetermined position serving as a center.
What is called an orbit machining that a main shaft turns around a predetermined center has been adopted as a method for forming an inner circumferential face and an outer circumferential face of a work into curved faces variously shaped like cylinders, tapered shapes, flanges, or the like, as disclosed in Patent Literature 1. This machining method is technically advantageous in that machining can be achieved at whatever position a table supporting the work is located.
A cutting velocity needs to be constant in order to provide an even cut face.
However, for the orbit machining method according to the related art as is described above, no configuration that makes a cutting velocity constant has been adopted.
Patent Literature 2 discloses a configuration, for cutting method of gear shaped object, needed to maintain a constant cutting velocity from a cutting start point to a cutting end point.
However, Patent Literature 2 only discloses that the cutting velocity is made constant simply under the control of an NC lathe and fails to clarify what qualitative or quantitative criteria are used to make a cutting velocity constant.
Patent Literature 3 discloses that a CAM controls the number of rotations of the main shaft to obtain a constant cutting velocity. However, Patent Literature 3 also fails to clarify a specific configuration concerning what criteria are used to make a cutting velocity constant.
Furthermore, Patent Literatures 2 and 3 are predicted on cutting based on rotation of the main shaft along a central shaft thereof and do not disclose or suggest that the cutting velocity is constant when the main shaft turns around a predetermined position serving as a center as is the case with the present invention.
Thus, for the cutting of the inner circumferential face or the outer circumferential face of the work based on turning of the main shaft, no cutting method has been proposed in which the cutting velocity of the cutting tool is controlled to be constant.
Patent literature 4 discloses that a cutting velocity of a cutting tool is set to be constant by changing ω according to a change of a distance R wherein ω is rotational angular velocity of a main shaft, R is the distance from a rotational center to a tip of the cutting tool, and constant value C is set as the cutting velocity in the tip of the cutting tool (paragraph [0040] and FIG. 7 (a) and (b)).
However, constant cutting velocity in patent literature 4 means that a value of R−ω is constant at most, and patent literature 4 does not disclose obtaining constant velocity with a factor of a time differential of the distance R.
So, patent literature 4 does not disclose the state of setting the cutting velocity accurately.